Method of making synthetic brushes



Nov. 22, 1949 E. H. HAUX 2,488,865

METHOD OF MAKING SYNTHETIC BRUSHES Filed June 2'7, 1944 awe/14M fZ/vEe/K Hnw/ Patented Nov. 22, 1949 UNITED STATES PATENT OFFICE METHOD OF MAKING SYNTHETIC BRUSHES Elmer H. Haux, Baltimore, Md., assignor to Pittsburgh ?late Glass Company, Allegheny County, Pa., a corporation of Pennsylvania Application June 2'7, 1944, Serial No. 542,321

4 Claims. 1

This invention relates to the manufacture of brushes and it has particular relation to methods of assembling and mounting synthetic bristles in brush structures.

One object of the invention is to provide an improved method of combining bristles into the form of a knot suitable for mounting as a unit upon a brush handle.

Another object of the invention is to provide an improved method of setting synthetic bristles preparatory to combining them with brush handles and ferrules.

In the manufacture of synthetic bristles for brushes, filaments are extruded from a solution of organic plastic through a spinneret and cut to proper length for incorporation in a brush structure. Suitable manufacturing processes for producing such bristles are disclosed in copending applications of John J. Gregory, Serial No. 459,251, filed September 22, 1942 (Patent 2,374,744 issued May 1, 1945) for Apparatus and process for tapering artificial filaments; and Serial No. 499,264, filed August 19, 1943 (Patent 2,356,841 issued Aug. 29, 1944) for Filament cutting apparatus,

According to the invention described herein synthetic bristles are assembled in knot form and the butts are dipped into a solution of resin of the same kind as that of which the bristles are formed. One end of the knot is thus welded into a matrix from which the bristles extend integrally. Ferrules are applied to the assembled bristles and secured to a brush handle. In one form of the invention blocks of wood or the like can be inserted at the base of the knot for separating the bristles and for defining a socket, when the blocks are removed, for fitting upon a brush handle, or the blocks can remain in the end of the knot for rigid support of the bristles in their assembly with the ferrule and handle.

In the drawing:

Fig. 1 is an edge elevation of a knot of bristles assembled for treatment according to the invention; Fig. 2 is a diagrammatic view partially in vertical section of supply means for solvent or solution in which the bristles are to be clipped; Fig. 3 is a fragmentary vertical section on a larger scale of a brush structure; Fig. 4 is a fragmentary vertical section of another form of handle assembled with a knot of bristles; Fig. 5

is a perspective of a knot of bristles assembled for fitting over a portion of a brush handle of the type shown in Fig. 4; and Fig. 6 is a diagrammatic perspective illustrating a brush knot with blocks partially removed therefrom.

In practicing the invention resinous bristles ID are assembled into the form of knots l2 as shown in Fig. 2, and in this form are dipped in a flax seed oil solution which serves to bind them to-. gether temporarily to facilitate the handling thereof. Blocks [4 of wood or the like are inserted in the ends or base portions of the knots and when removed the blocks define sockets l5 as shown in Figs. 5 and 6, or the blocks can remain in place to serve as separators oi bristles in the base portion of the knot as shown in Fig. 3. Each knot thus assembled with the blocks I4 is dipped in a solution [6 of resin of the same kind as that of which the bristles are formed and containing a solvent for the bristles. For example, suitable bristles are composed of cellulose triacetate extruded usually in tapered form and cut to length in the manner specified in the copending applications above identified.

The solution It is contained in a tank l8 and the knots are placed upon a perforated support l9, the upper portion of which can be in the form of a screen to facilitate access of the solution to the ends of the bristles. The level of the solution is controlled by a valve 2!: in a conduit 2! communicating with the tank l8 and with a suitable supply reservoir 23. The knots rest upon the support in such manner that their base portions are slightly submerged in the solution to a depth of approximately of an inch or less.

A solution suitable for the purpose specified consists of 3 percent to 4 percent cellulose triacetate in tetrachlorethane, the latter of which is a solvent. The viscosity of this solution at room temperature F. to F.) is such that during the setting period the solution is drawn by capillary attraction uniformly between the bristles to a height of approximately A; of an inch in eight to twelve minutes. A solution of greater or lesser viscosity can be employed. If a solution of lesser viscosity is used a shorter period of setting is required but, in the latter, the action upon the bristles is more diificult to control. This solution wets and softens the butt of each bristle.

At the completion of the softening period in the solution, the knots of bristles are removed and permitted to drain for several minutes. They are then placed in an oven where they are subjected to a temperature of 225 to 250 F. for 3 to 5 hours. As a result of this heat treatment the solvent is driven 01f or evaporated and the base portions of the bristles which were wet are welded together in a homogeneous mass or 3 matrix of cellulose acetate. The bristles project integrally from this homogeneous mass. Socalled burrs or swelling may result from this treatment and such burrs can be removed by buffing or sandpapering.

Each knot can then be forced into a ferrule 30 and nailed. thereto, as indicated at 3|, with the blocks l4 remaining in place. In order to produce a more compact structure and a closely fitting relationship of parts, the assembled knot and ferrule are inverted and a relatively thin solution of plastic is poured along the junction of the knot and ferrule so as to penetrate and fill in interstices that may have existed at this location. A suitable solution for this purpose consists of the following:

Parts Cellulose triacetate 50 Tetrachlorethane 50 Methylene chloride 400 Methylene chloride has a relatively low boiling point and because of this fact and the fact that a high percentage of this substance is included in this solution, the latter stiflens rapidly when exposed to atmospheric air. Therefore, the solutions flows into the interstices and serves as a self-sealing agent between the knot and ferrule. The solution becomes set before it can spread to the shanks of the bristles.

Obviously practice of the invention is not limited to the use of bristles of any particular plastic, or ,to the use of any particular solvent for the plastic. For example, the bristles may be of cellulose acetobutyrate for which methyl chloride is a satisfactory solvent.

The butts of nylon or polyamide bristles can be softened and welded by application of xylenol, cresol, formic acid or the like as softening agents.

Bristles of Saran or polymerized vinylidene chloride may be employed and can be caused to weld by application of solvents such a cyclohexanone, dioxane or dichlorodiethyl ether or the like.

The knots treated and assembled as described above are permitted to set for 15 to 20 minutes and then a brush handle 34 (Fig. 3) is forced into the ferrule and nailed thereto, as indicated at 35.

Another form of brush handle 4!] (Fig. 4) is so formed that it has tongues M of the same general outline as the blocks l4. Upon removal of these blocks from the knot to form sockets as shown in Figs. 5 and 6, the tongues of the handle are forced into the sockets [5 in conjunction with the fitting of the ferrule 43 thereon. The latter is nailed, as indicated at 45, to the handle and knot.

If desired the ferrule 43 can be in the form of a plastic band which is applied by bonding to the handle and to the base of the knot.

Although only illustrative forms of the inven-- tion have been shown and described in detail it will be apparent to those skilled in the art that the invention is not so limited but that various changes can be made therein without departing from the spirit of the invention so long as such changes are within the scope of the appended claims.

What I claim is:

1. In a method of setting synthetic bristles of at least partially soluble organic plastic to form a brush knot having a base portion, the steps which comprise assembling a group of synthetic bristles into the form of a knot with end portions of the bristles surrounding a removable block to define a socket in the base portion of the knot, dipping the base portion of the knot thus assembled with the block in a bath capable of at least partially dissolving the bristles to form a matrix for the bristles, removing the knot from the. bath and drying it to form a homogeneous mass at said base portion from which each bristle extends as an integral element.

2. In a method of making brushes, the steps which comprise assemblin synthetic bristles of at least partially soluble organic plastic into the form of a knot with portions of the bristles surrounding a block to define a socket in an end portion of the knot, dipping the end of the knot thus assembled with the block in a bath containing a solvent for the bristles to soften the latter, driving off the solvent from the softened bristles and Welding the latter into a homogeneous matrix from which the shanks of the bristles project integrally, and removing the block from the end of the knot to expose a socketed portion capable of fitting upon a brush handle.

3. In a method of making brushes, the steps which comprise assembling synthetic bristles composed essentially of cellulose triacetate into the form of a bristle knot with an end portion of the knot plugged by a removable block to define a socket when the block is removed, dipping the plugged end of the knot into a setting solution of 3 percent to 4 percent cellulose triacetate in tetrachlorethane at least partially to dissolve the dipped end portion of the knot, removing the clipped bristle knot and drying it in a heated oven to weld the dipped ends of the bristles into a homogeneous mass from which the bristles extend integrally, removing the block, and assembling the knot so formed upon a brush handle.

4. In a method of making brushes, the steps which comprise assembling synthetic bristles composed of at least partially soluble organic plastic into the form of a bristle knot with an end portion of the knot plugged by a removable block to define a socket when removed, dipping the plugged end of the knot into a setting solution of organic plastic capable of softening said bristles by dissolving action and permitting the bristle ends to remain in thesolution until they become softened, removing the clipped softened bristle knot and drying it in a heated oven to weld the dipped ends of the bristles into a homogeneous mass from which the bristles extend integrally, removing the block, and assernbying the knot so formed upon a brush handle.

ELMER H. HAUX.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,202,244 Timmis Oct. 24, 1916 1,238,635 Chandler Aug. 28, 1917 1,775,968 Dreyfus Aug. 26, 1930 1,871,046 Dickie Aug. 9, 1932 1,912,625 Dreyfus June 6, 1933 1,923,322 Mendel Aug. 22, 1933 2,030,160 Titcomb Feb. 11, 1936 2,303,800 Swann Dec. 1, 1942 

